1. Field of the Invention
The present invention relates to a communication light detecting device provided at a portion where light transmission paths are interconnected and, in particular, relates to a communication light detecting device which is able to confirm the communication state in the transmission paths. Further, the present invention relates to a communication light detecting device provided at a portion where light transmission paths are interconnected and, in particular, relates to a communication light detecting device which is able to detect a failure of the a communication light detecting device itself.
2. Description of Related Art
Recently, in a field of information (data) communication, optical fibers, which allow a high speed and large capacity transmission, for transmission lines are used as a main stream so as to cope with an increase of data amount to be communicated. In response thereto, in particular, in facilities relating to optical communication such as data center and communication station, works such as alternation and extension of light transmission paths are frequently performed.
Since communication light that communicates back and forth in a light transmission path is invisible light, existence and absence of communication cannot be confirmed visibly. For this reason, workers such as a person for maintenance or for operation of a light communication facility cannot easily grasp an operating condition whether a light transmission path in the installation is in use or not. As a result, such problems arose that work efficiency reduces due to requirement of an extra time for grasping the operating condition of the light transmission path (for example, discrimination of in use/not in use) and an erroneous manipulation of pulling out an optical connector occurs due to erroneous recognition of a condition of the light transmission path where communication light is being transmitted, as a condition of no communication light being transmitted.
In order to enhance maintenance performance and operation efficiency of a light communication facility while preventing the above referred to erroneous manipulation, a variety of measures have been investigated which are able to recognize visibly existence and absence of invisible communication light under a condition where such as optical fibers and optical connectors are interconnected. For example, JP-A-2004-170488 proposes an optical fiber connector in which ferrules building in an optical fiber are used, when butt contacting the ferrules in a divided sleeve. A gap between the end faces of the ferrules is formed, a wave guide substance consisting of light transmittable resin is provided in the gap, a part of communication light is guided via the wave guide substance to a fluorescent substance to cause the fluorescent substance to generate visible light, and thereby, existence and absence of communication light can be visibly confirmed.
JP-A-2004-133071 and JP-A-2003-218813 propose such as an light signal detecting part and a light signal monitoring device in which a light branching means such as an optical wave guide channel substrate is disposed between two ferrules building in an optical fiber are used, and the light branching means branches a part of communication light and guides the same to such as a communication light output portion and a visible light conversion element, and through converting a part of branched communication light into visible light, existence and absence of communication light in the optical fiber can be confirmed.
JP-A-2002-214487 proposes a light monitoring device in which branching faces are formed by polishing end faces of two optical fibers respectively at 45 degrees, a branching film (filter) is sandwiched between the branching faces and a part of communication light reflected by the branching film is detected by a PD (photo diode) to light on an LED (light emitting diode). Besides, JP-A-2004-177549 (US 2004/0208458 A1) proposes a bi-directional optical module in which a light receiving portion is constituted in such a manner that a core of an optical fiber is cut so as to cross diagonally and a light output portion is formed by inserting between the cut faces a filter or a half mirror for reflecting a part of communication light, then the light output portion is photo coupled with a light receiving element, and the optical fiber end portion of the thus constituted light receiving portion is configured so as to permit interconnection with an optical connector via a ferrule.
Prior arts referred to above respectively have the following drawbacks. For example, the optical fiber connector disclosed in JP-A-2004-170488 possesses a problem that because the wave guide substance is provided in a very narrow gap, a highly accurate positioning technique (for example, such as adjusting length of the gap while measuring a loss of the communication light by making use of a power monitor) for the assembly is required which likely increases the manufacturing cost. Furthermore, since the ferrule building in an optical fiber is secured by such as pressure bonding, because of stress variation due to insertion and disinsertion of the ferrule, the wave guide substance consisting of a resin and provided in the gap is possibly peeled off which arises a task with regard to reliability in long term. Moreover, since the light detecting substance is fluorescent substance, the light emitting time thereof is extremely short which makes the visual recognition difficult.
Also, the light signal detecting part disclosed in JP-A-2004-133071 possesses a problem that because the optical fiber in the ferrule, the optical wave guide channel substrate and the communication light output portion are required to be interconnected to match their optical axes, a highly accurate positioning technique for the assembly is required which likely increases the manufacturing cost. Furthermore, the members such as the optical wave guide channel substrate are expensive, which causes a problem of blocking cost reduction as a whole. The light signal monitoring device disclosed in JP-A-2003-218813 possesses a problem that since the light emitting is effected only when the light signal is reaching at the visual light converting element, the light emitting time thereof is thought extremely short which makes the visual recognition difficult.
Such as the light monitoring device and the bi-directional optical module disclosed in JP-A-2002-214487 and JP-A-2004-177549 (US 2004/0208458 A1) respectively possess a problem that since such as the filter and the half mirror are used for reflecting and branching the communication light, a highly accurate positioning technique for preventing reduction of the detection sensibility of the communication light caused in association with the increase of the number of parts is required, which likely increases the manufacturing cost.
In addition to the above, when the communication light detecting device itself fails, since the communication light detecting device cannot detect communication light transmitting through the light transmission path, a problem arises whether the communication light is transmitted or not, and that the information cannot be conveyed to a concerned worker. Namely, a problem arises that the worker cannot correctly recognize the existence and absence of the communication light. No countermeasures with regard to such failure of the communication light detecting device are disclosed in the above patent documents.